Twenty Indian soldiers were killed during a "violent face-off" with Chinese troops on the contested border in the Himalayas, the Indian Army said in a statement on Tuesday regarding the first such incident between the two countries in 45 years.

Tensions have been growing on the long-disputed Himalayan border since last month, with both New Delhi and Beijing accusing the other of crossing the 3,488-kilometer-long Line of Actual Control that separates the two sides.

Indian soldiers erect a military bunker along the Srinagar-Leh National highway on June 16, 2020. During the de-escalation process underway in the Galwan Valley, a violent face-off took place between Indian and Chinese soldiers with casualties.  (Getty/Kyodo)

"Seventeen Indian troops who were critically injured in the line of duty at the stand-off location and exposed to sub-zero temperatures in the high altitude terrain have succumbed to their injuries, taking the total that were killed in action to 20," the statement said, referring to the clash on Monday night.

A spokesperson for India's External Affairs Ministry said in a statement on Tuesday, "On the late-evening and night of June 15, a violent face-off happened as a result of an attempt by the Chinese side to unilaterally change the status quo there."

"We remain firmly convinced of the need for the maintenance of the peace and tranquility in the border areas and the resolution of differences through dialogue. At the same time, we are also strongly committed to ensuring India's sovereignty and territorial integrity."

The incident occurred "during a de-escalation process under way in the Galwan Valley," the Army said earlier on Tuesday, adding that senior military officials of both sides are currently meeting to "defuse the situation."

Meanwhile, China also criticized India over the clash, with its Foreign Ministry spokesman Zhao Lijian saying on Monday that the Indian side "seriously violated our consensus and crossed the border line twice for illegal activities and provoked and attacked Chinese personnel which lead to serious physical conflict between the two sides."

While Zhao did not confirm any casualties on the Chinese side, the editor-in-chief of China's Global Times newspaper later said the Chinese side also suffered casualties in the clash but cannot yet confirm the number.

The Press Trust of India reported that among the fatalities was the commanding officer of the army battalion at Galwan. It said no gunshots were fired and they likely died of injuries sustained following stone-pelting by the Chinese side.

Four Indian soldiers were killed in an ambush along the de facto border in 1975.